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Date:   Mon, 3 Jul 2023 08:45:38 -0600
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Subject: Re: Memory providers multiplexing (Was: [PATCH net-next v4 4/5]
 page_pool: remove PP_FLAG_PAGE_FRAG flag)
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To:     Mina Almasry <almasrymina@google.com>
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From:   David Ahern <dsahern@kernel.org>
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On 7/3/23 12:22 AM, Mina Almasry wrote:
> tcpdump is able to access the header of these skbs which is in host
> memory, but not the payload in device memory. Here is an example
> session with my netcat-like test for device memory TCP:
> https://pastebin.com/raw/FRjKf0kv
> 
> tcpdump seems to work, and the length of the packets above is correct.
> tcpdump -A however isn't able to print the payload of the packets:
> https://pastebin.com/raw/2PcNxaZV

That is my expectation. The tcpdump is just an easy example of accessing
the skb page frags. skb_copy_and_csum_bits used by icmp is another
example that can walk frags wanting access to device memory. You did not
cause a panic or trip a WARN_ON for example with the tcpdump?

Thanks for checking.